This is treated by NABA as Callophrys dumetorum viridis, and a subspecies of Bramble Hairstreak. Others have stated that viridis is an invalid name that should properly be dumetorum, consequently referring to Coastal Green Hairstreak as Callophrys dumetorum, while Bramble Hairstreak receives the scientific name of C. perplexa. At any rate, the visual differences between this and the Bramble Hairstreak are very striking!

GreenHairstreak2.jpg
San Bruno Mountain, San Mateo County, CA, 3/2/2003
GreenHairstreak3.jpg
San Bruno Mountain, San Mateo County, CA, 3/2/2003